Plagiodera versicolora (Laicharting, 1781)
A locally common species throughout the southeast north to the Humber and west to Somerset and south Wales, there are a few records from southeast Yorkshire (Cox). The host plant is usually Salix fragilis (Crack Willow) although it is also found on other Salix spp. and has been recorded from Populus nigra (Atty ¹) and Betula (Fowler, 1890). Adults overwinter under logs, loose bark and among vegetable litter near the host and become active during the first warm days of april, coinciding more or less with the emergence of Salix foliage. They soon become common and from may onwards can be swept or beaten from Salix throughout our area. Adults feed on the underside of the leaves producing small holes. Larvae often occur in groups and may skeletonise leaves, fully developed larvae may be found from mid june onwards and pupation occurs under the leaves. Freshly emerged adults occur from mid july (Cox). Adults fly in hot weather and are occasionally found far from their hosts, especially along river margins e.g. along the Colne at Radlett road, and on one occasion (june 2006) we found hundreds swarming on aluminium railings beneath several large Salix fragilis at Cassiobridge.

Of a similar size and colour to Phaedon spp. with which it may be confused in the field but readily distinguished under a X10 lens by the random elytral punctuation.

2.5-4.5mm. Entire upper surface dark metallic blue or green, rarely black. Varies considerably in fine detail. Antennae black with basal four or five segments to some extent dark yellow, at least beneath. Inserted under side of head in front of eyes and separated by at least twice the length of segment one. Puncturation and sculpture of head varies from finely and sparsely to quite coarsely punctate and from smooth and shiny to rugose, variously depressed between eyes. Posterior margin of eyes hidden under pronotum. Pronotum strongly transverse with prominent front angles, finely bordered, usually very finely so along hind margin. Smoothly rounded laterally or sinuate behind front angles. Puncturation varies from very finely punctate on a smooth and shiny cuticle with coarser punctures laterally to entirely coarsely punctate on a dull cuticle becoming rugose laterally. Scutellum impunctate and shiny, central area often raised and with various depressions. Elytra almost quadrate (Average L65:W58), strongly bordered laterally, more finely so along base and with strong humeral prominence. Puncturation random although there is a tendency to form short rows, these will not be taken for striae. Much finer puncturation often visible. Surface varies from smooth and shiny to somewhat dull due to fine 'wrinkles' around the large punctures. Legs dark, tarsi usually indistinctly lighter and claws yellow. Tibiae gradually thickened towards apex, without apical tooth on outer edge.
The above description is from 5 watford specimens at X20.

¹ Atty, D.B. 1983. Coleoptera of Gloucestershire. Cheltenham; privately published. See Cox 2007